java - 重复 doGet 调用

Question

我的 HttpServlet 片段:

   protected void doGet(HttpServletRequest httpServletRequest,
                         HttpServletResponse httpServletResponse) throws ServletException,
                                                                         IOException {
        final String[] values = httpServletRequest.getParameterValues("p");
        final int p;
        if (values != null && values.length > 0) {
            p = Integer.parseInt(values[0]);
        } else {
            p = 0;
        }
        final ServletContext context = super.getServletContext();
        switch (p) {
        case 0:
            {

                final CityRepresentationBean bean =
                    new CityRepresentationBean(ds);
                final RequestDispatcher rqDsp;
                try {
                    rqDsp =
                            context.getRequestDispatcher(bean.act(httpServletRequest));
                    rqDsp.forward(httpServletRequest, httpServletResponse);
                } catch (ConnectionException e) {
                    throw new ServletException(e);
                }
 ......
}

主要问题是我收到 StackOverFlow 异常。从调试中，我发现我得到 ConnectionException，然后在 抛出 new ServletException(e) 之后再次调用 doGet 方法(我什至不知道谁可以调用它)。

问题是如果浏览器只调用一次 URL，如何多次调用 servlet？

java.lang.StackOverflowError
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
    at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:303)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
    at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
    at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
    at project2.FrontController.doGet(FrontController.java:64)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
    at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
    at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
    at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
    at project2.FrontController.doGet(FrontController.java:64)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
    at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
    at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
    at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
    at project2.FrontController.doGet(FrontController.java:64)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
    at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
    at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
    at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
    at project2.FrontController.doGet(FrontController.java:64)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227)
    at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:300)
    at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
    at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
    at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
    at project2.FrontController.doGet(FrontController.java:64)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)

Answer 1

该 servlet 的 URL 模式也与 bean.act(httpServletRequest) 返回的 URL 相匹配。在你的RequestDispatcher#forward() .

所以，你有两个选择:

1. 将 servlet 映射到更具体的 URL 模式。至少/*上不或者其他的东西。例如，/pages/*或*.do .
2. 确保 act() 返回的 URL与 servlet 的 URL 模式不匹配。

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